In general, when transmitting any signal via different transmission routes, a non-ideal transmission channel must be assumed. In travelling to the receiver, the signal may be attenuated and reflected, e.g., at connection points or obstacles. In the case of time-discrete systems, this signal is sampled in an A-D converter with a fixed clock pulse, synchronised by re-sampling at the n-fold multiple of the sampling rate (and/or of the symbol pulse) and the relevant signal level is allocated to a symbolic value. If the transmission channel is non-ideal, this leads to small eye-openings and, in extreme cases, to an incorrect symbol allocation. In order to compensate linear errors of the transmission channel, a receiver must contain an equaliser. This provides a system behaviour, which, in the case of an exact compensation of the linearity error, operates in an exactly inverse manner to the transmission behaviour of the transmission channel.
To improve the quality of reception of the transmitted message, general measures for the removal and/or restriction of transmission interference must be implemented alongside continuous compensation of the linearity error with an equaliser integrated in the receiver.
Suggested solutions, which represent the state of the art in this context, are presented in a textbook by K. D Kammeyer, “Nachrichtenabertragung” [Message Transmission] ISBN 3-519-16142-7. Stuttgart, 1996, pages 196-205. With these suggested methods, the coefficients of a series-connected equaliser required for optimum equalisation are calculated via iterative optimisation algorithms on the basis of pseudo-random sequences of transmission data and the associated data sequences received at the end of the transmission channel. A two-stage method, wherein the channel impulse response is determined in a first stage, and, the coefficients of the channel transmission function, which are in mirror-image to the coefficients of the equaliser in the case of an exact equalisation of the transmission channel, are calculated from the channel impulse response, in the second stage, does not exist.